feat(vector-io): add OpenGauss vector database provider

Implement OpenGauss vector database integration for Llama Stack with the following features:
- Add OpenGaussVectorIOAdapter for vector storage and retrieval
- Support native vector similarity search operations
- Provide configuration template for easy setup
- Add comprehensive unit tests
- Align with the latest Llama Stack provider architecture, including KVStore and OpenAI Vector Store Mixin.

The implementation allows Llama Stack users to leverage OpenGauss as an
enterprise-grade vector database for RAG applications.

docs/source/providers/vector_io/remote_opengauss.md

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+# remote::opengauss
+
+## Description
+
+
+[OpenGauss](https://opengauss.org/en/) is a remote vector database provider for Llama Stack. It
+allows you to store and query vectors directly in memory.
+That means you'll get fast and efficient vector retrieval.
+
+## Features
+
+- Easy to use
+- Fully integrated with Llama Stack
+
+## Usage
+
+To use OpenGauss in your Llama Stack project, follow these steps:
+
+1. Install the necessary dependencies.
+2. Configure your Llama Stack project to use OpenGauss.
+3. Start storing and querying vectors.
+
+## Installation
+
+You can install OpenGauss using docker:
+
+```bash
+docker pull opengauss/opengauss:latest
+```
+## Documentation
+See [OpenGauss' documentation](https://docs.opengauss.org/en/docs/5.0.0/docs/GettingStarted/understanding-opengauss.html) for more details about OpenGauss in general.
+
+
+## Configuration
+
+| Field | Type | Required | Default | Description |
+|-------|------|----------|---------|-------------|
+| `host` | `str \| None` | No | localhost |  |
+| `port` | `int \| None` | No | 5432 |  |
+| `db` | `str \| None` | No | postgres |  |
+| `user` | `str \| None` | No | postgres |  |
+| `password` | `str \| None` | No | mysecretpassword |  |
+| `kvstore` | `utils.kvstore.config.RedisKVStoreConfig \| utils.kvstore.config.SqliteKVStoreConfig \| utils.kvstore.config.PostgresKVStoreConfig \| utils.kvstore.config.MongoDBKVStoreConfig, annotation=NoneType, required=False, default='sqlite', discriminator='type'` | No |  | Config for KV store backend (SQLite only for now) |
+
+## Sample Configuration
+
+```yaml
+host: ${env.OPENGAUSS_HOST:=localhost}
+port: ${env.OPENGAUSS_PORT:=5432}
+db: ${env.OPENGAUSS_DB}
+user: ${env.OPENGAUSS_USER}
+password: ${env.OPENGAUSS_PASSWORD}
+kvstore:
+  type: sqlite
+  db_path: ${env.SQLITE_STORE_DIR:=~/.llama/dummy}/opengauss_registry.db
+
+```
+